1. Field of the Invention
The present invention relates to a synchronous digital hierarchy digital cross-connection apparatus (hereinafter, referred to as SDHDXC), which strengthens a signal supervision function.
The present application for the synchronous digital hierarchy digital cross-connection apparatus, is based on Korean Application which is incorporated herein by reference for all purposes.
2. Description of the Related Art
In general, the apparatus according to the present invention is connected to an optical cable to which an optical signal STM-N being a synchronous signal, described in ITU-T Recommendation G.707.about.G.709, is transmitted, and receives the cable signal STM-N to thereby perform data recovery and clock extraction through an optical to electrical conversion. Thereafter, the apparatus of the present invention processes section overhead SOH separately from payload after descrambling and reframing for the cable signal STM-N. Further, the apparatus in accordance with the present invention is intended to extract an AU signal from the separated STM-N payload and realign each frame phase by means of the same reference timing for executing a cross connect switching XCS operation by the AU. Then, the switched AU signal is multiplexed into the STM-N, together with the section overhead SOH, and converted into the optical signal to be transmitted to the optical cable. Furthermore, the apparatus of the present invention detects an unoccupied signal by supervising the AU signal input to the switch and releases a connection with the switch of a corresponding signal channel to thereby perform a signal end process. Moreover, the apparatus according to the present invention is intended to manage an unconnected signal state where the switching operation is released by supervising a signal to be output from the switch so that it is possible to switch a path of the synchronous signal and to smoothly perform a function of a digital cross connection.
In the present invention, a spare channel should always be surpervised and managed for protection so that a reconstruction and recovery operation can be performed when a transmission network railroad/path is disconnected in the synchronous transmission network to which the SDHDXC apparatus of the present invention is applied. Thereby, it should be necessary to thoroughly maintain the unconnected signal under supervision of a signal connecting state to be performed by the switched AU signal in front-end and post-end terminals of the cross connection switch.